US3052100A

US3052100A - Refrigeration system

Info

Publication number: US3052100A
Application number: US51220A
Authority: US
Inventors: Bartell J Homkes
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1960-08-22
Filing date: 1960-08-22
Publication date: 1962-09-04
Anticipated expiration: 1979-09-04

Description

Sept. 4, 1962 B. J. HOMKES REFRIGERATION SYSTEM 2 Sheets-Sheet 2 Filed Aug. 22, 1960 INVENTOR.

II'A

VIII'III FIG. 4

Barre/I J. Homkes Unite xii This invention relates to electric refrigerators and in particular to refrigerators utilizing a combination of conventional refrigeration apparatus and thermoelectric refrigeration apparatus.

It is a general object of the invention to provide a domestic refrigerator of the type using any conventional refrigeration system such as the compression-condensation-expansion system or an absorption system, with added thermoelectric facilities for specific purposes within the refrigerator cabinet. It is a specific objective of the invention to provide a novel means for dissipating the heat from the hot junction of a thermoelectric pile embodied in a conventional refrigerator.

It is a further object of the invention to dissipate the heat generated at the hot junction of a thermoelectric pile in a manner which is advantageous to the operation of a conventional refrigeration system.

It is well known in the art of domestic refrigeration that it is quite dificult to utilize the refrigerant circuit of a conventional system in a manner which provides a proper operational balance between fresh food storage capacity, which ordinarily requires temperature in the ranges between 36 and 40 F., and compartments which require different temperatures, such as an ice making compartment or a meat storage compartment, for example.

Pursuant to the present invention, the necessary temperature requirements of such specialized uses may advantageously be obtained by providing within a conventional refrigerator, special purpose compartments which are equipped with a thermoelectric pile utilizing the well known Peltier effect to accomplish the necessary heat transfer. Such an arrangement simplifies the conven tional refrigeration circuit and requires it to do but a single refrigeration job. A practical difficulty in the use of a thermoelectric pile within a refrigeration cabinet arises with respect to the removal of the heat generated at the hot junction of the thermoelectric elements. If this heat is permitted to escape into the food storage chamber, it will obviously increase the temperature thereof and may interfere with the air circulation within the chamber. Dissipation of heat to the ambient air requires that the thermoelectric units be located where this can be done expeditiously and such locations may be incompatible with the most effective placement of the thermoelectric pile with respect to its intended purpose.

In its preferred forms, the present invention contemplates an arrangement pursuant to which the heat to be dissipated is used in refrigeration locations where it is common to use electric resistance heat. For example, it is conventional to use resistance heating about the cabinet opening to maintain that portion of the cabinet above the dew point and thus prevent condensation or sweating about the door. As presently described, the thermoelectrically heated compartments are arranged with heat exchange systems capable of putting the otherwise wasted heat to this useful purpose.

Other features and advantages of the invention will be understood from the following description of preferred embodiments thereof read in connection with the accompanying drawings in which:

FIG. 1 is a vertical front elevational section of a refrigerator embodying a meat storage compartment utilizing the present invention;

"ice

FIG. 2 is a side sectional elevation thereof taken on lines 2-2 of FIG. 1;

FIG. 3 is a fragmentary perspective of the meat storage compartment showing an arrangement of the thermoelectric system in one of the side walls thereof;

FIG. 4 is a horizontal section of a side wall of the meat storage compartment looking in the direction of the arrows 44 of FIG. 2;

FIG. 5 is a fragmentary side sectional elevation showing a second embodiment of the invention;

FIG. 6 is a vertical section of the embodiment of FIG. 5 looking in the direction of the arrows 66 of FIG. 5;

FIG. 7 is a fragmentary perspective of a refrigerator door incorporating a thermoelectrically cooled compartment for the storage of packages or containers of frozen food; and

FIG. 8 is a schematic temperature control circuit for the meat storage compartment.

FIGS. 1 through 4 are descriptive of an embodiment of the invention in which a thermoelectric heat transfer system is used to abstract heat from a compartment in the lower portion of the cabinet within which meat is to be stored. The heat from the hot side of the system is distributed about the front peripheral wall of the cabinet. The refrigerator is of the type in which the principal storage chamber is devoted to the storage of fresh foods whereupon the chamber temperature would be in the normal range of from 35 to 40 F. Obviously, the refrigerator is not necessarily restricted to this type. Although the refrigerator system for this purpose may be of the conventional absorption or compressor type it has been illustrated as being the latter. The cabinet 1 has an inner liner 2 defining the fresh food storage compartment 3. Below this compartment is a chamber 4 in which the thermoelectric systems presently described maintain a chamber temperature suitable for the storage of fresh meats. Such temperatures are advantageously close to the freezing temperature of water, that is to say, in the range of 3 -35" F. The chamber 4 may, for example, be of a suitable moulded plastic supported relative to chamber 3 and the outer casing 5 by any suitable brackets 6, 7 which may be of any appropriate material to restrict heat exchange between the compartment 4 and the outer cabinet structure 5. Said brackets may extend between the chamber 4 and the outer casing 5 and a bottom casing plate 8. Chamber 4 is formed with a flange 10 at both sides and the bottom. This flange provides a continuation of the usual breaker strip (not shown) by means of which the front edges of the inner and outer cabinet portions are joined to define a forward wall against which the conventional door 11 seats. The usual sealing gasket 12 is provided about the periphery of the door. The wall 8 and outer casing 5 define a suitable compartment 14 within which are placed the compressor 15 and the condenser 16. As is well known in the art, a suction tube 17 conveys gaseous refrigerant from the evaporator 18 to the compressor. Hot compressed gas from the compressor flows to the condenser 16 by appropriate tubing (not shown). Liquid refrigerant is transmitted from the condenser to the evaporator by way of a tube system 19 which may include a restrictor portion of capillary tubing or any suitable expansion valve (not shown) as well known in the art. The suction tube 17 and the tube system 19 are principally located within the insulation 29 which envelops the chamber 3 and compartment 4. Any conventional thermostat (not shown) responsive to the air temperature within chamber 3 may be used to cycle the operation of the compressor to maintain the desired chamber temperature, as well known in the art.

FIGS. 3 and 4 disclose in section the thermoelectric pile which in duplicated at each of the side walls of the compartment 4. Together the thermoelectric piles are calculated to maintain a temperature of between 33 and I 35 F. in compartment 4. Each of the thermoelectric piles includes a plurality of thermocouples each providing a hot junction and a cold junction when direct current electric energy is applied thereto. The cold junctions are in the interior side wall surfaces of compartment 4 and the hot junctions are on the exterior wall surfaces. To accommodate the multiplicity of thermocouples required to effect the necessary heat transfer, the side walls of the chamber 4 are provided with apertures arranged in horizontal rows. Specifically, in the odd ones of these apertures there are arranged P-type semiconductor 20 and in the even ones of these apertures there are arranged N-type semiconductors 21. In the outermost or right hand side wall as viewed in FIG. 3, an arrangement of electrically conductive copper bus bars 22 provides for a series electrical connection between the succession of P- and N-type units and on the inner wall an arrangement of copper bus bars 23 forms a similar series connection between the semiconductors. The required electrical connections may be made by aperturing the bus bars to accommodate solder deposits or equivalent. According to the arrangement of apertures in the side walls the thermocouples are arranged in vertically spaced horizontal rows, each row being connected in parallel electric circuit arrangement by a lead 24 which connects all of the P-type semiconductors 20 in the front vertical row and a lead 25 which connects all of the N-type semiconductors 21 in the rearmost vertical row. It will thus be observed from FIGS. 3 and 4 that the first of the P-type units 20 is connected to the conductor 24 and is connected by the conductor 22 to the first of the N-type units 21. In turn, this unit 21 is connected by the conductor 23 to the next succeeding P-type unit 20 and so on until the penultimate P-type unit 20 is connected by way of bus bar 23 to the ultimate N- type unit 21. The

respective conductors

24 and 25 are advantageously placed in channels provided in the wall of chamber 4. Pursuant to this arrangement when a relatively positive potential is connected to the front P-type units 20 and a relatively negative potential is. connected to the rear N-type units 21 all of the connectors 23 between the

units

20 and 21 will comprise cold junctions of the thermoelectric pile and all of the connections 22 between the

units

20 and 21 will constitute hot junctions. The several bus bars and

connections

24 and 25 are amply sized for minimum electrical resistance, whereby to substantially eliminate the Joule heating thereof.

In order to improve the heat transfer from the respective groups of

conductors

22 and 23 while at the same time providing adequate electrical insulation for said conductors each of the faces of each side wall of the compartment 4 has applied thereto a laminated cover 26 in which a sheet 27 of aluminum or other good heat conducting material is coated with a thin layer 28 of a heat conducting and electrically insulating material such as the tetra-fluoroethylene product, known by the trade name Teflon. This Teflon layer is adhesively attached to the

adjacent conductors

22 or 23 to provide an insulating coating thereon while aifording adequate heat transfer. To the outermost or right hand aluminum sheet 27 as viewed in FIG. 3 there is brazed or otherwise secured in good heat transfer relation a loop 30 of a heat transfer system 30.1 which encircles the cabinet immediately behind the breaker strip thereof. This loop 30 has a charge of difluorodichloromethane refrigerant known by the trade name Freon and under normal application, the loop 30 will be occupied by liquid refrigerant up to just below the top of comparement 4, whereupon this loop 30 receives heat from the plate 27. The refrigerant is evaporated in the loop portion and condenses in the cold area of the system 30.1 about the front of the cabinet whereupon the heat of condensation warms this critical cabinet area to prevent condensation of atmospheric moisture. The condensed refrigerant returns to the loop 30 for reevaporation. Each of the semiconductors 20 is formed essentially of Bi Te which contains a small controlled amount of an acceptor impurity to render it a P-type semiconductor and each of the semiconductors 21 is formed essentially of Bi Te and contains a small controlled amount of donor impurity to render the same an N-type conductor. Ordinarily, the donor for an N-type unit is selected from the group consisting of P, As, and Sb; and ordinarily, the acceptor impurity for a P-type unit is selected from the group consisting of B, Al, Ga, and In. Each of the N-type units is of cylindrical form having a length of 1 cm. and a cross sectional area of 1.0 cm. Each of the P-type units has a length of 1 cm. and a cross sectional area of 1.1 cm. Cumulatively the arrangements of thermocouples in the side walls of chamber 4 must provide suflicient cooling effect for cooling any food placed Within the chamber 4- and each of the thermocouple arrangements will deliver heat tothe loop 30 which is equal to the DC. power loss in the individual thermocouples and bus bars plus the heat removed from the contents of compartment 4. It is believed that under normal operating conditions, each thermocouple will have a figure of merit of approximately 2.8 l0= C.)- to achieve an average cooling effect of 1.25 watts with a power input of about .75 watt; and each thermocouple will have an average heat output of the order of 2 watts. In the average large size domestic refrigerator, the compartment 4 will have interior dimensions of approximately 12" height, 28" width, and 16" depth. In such a situation, a total of about thermocouples should produce about watts of cooling effect and 160 watts of heating eflect, whereupon in each of the side walls of the compartment 4 there will be arranged four rows of 10 thermocouples each. The heating eifect of the thermoelectric system, considering certain inefiiciencies such as heat loss within the walls of the cabinet, etc. will maintain a door opening temperature adequate to prevent sweating. Nevertheless, and despite the fact that the heat dissipation system is wholly within the cabinet, there is no noticeable increase in the temperature of the chamber 3 by virture of the operation of the thermoelectric piles.

It is contemplated that the service to which the compartment 4 will normally be put will produce varying heat loads as the door 11 is opened to permit access to the interior of the refrigerator and compartment and as food stuflfs are added to the contents thereof, and means are provided to maintain temperature control of the compartment within very close limits. Accordingly, as schematically shown, there is disposed within compartment 4 as by means of a ventilated casing 32 suitably secured to the top inner wall surface of the compartment, a low amplitude bimetal thermostat 33. As shown in FIG. 8, this is of the single pole, double throw type. Its bimetal components are arranged so that as the thermostat warms it deflects upwardly to close with the upper contact 34 and as it cools it deflects downwardly to close with the lower contact 35. In other words, the thermostat is always in a position at which it has closed with either the contact 34 or the contact 35. As is well known in the art, thermoelectric systems require a source of direct current of relatively low voltage-for example, of the order of 20 v. The energizing the control circuit therefore includes a step down transformer 36 of which the primary winding is supplied from the usual v. A.C. domestic source, there being any suitable manually operable switch (not shown) in this circuit. The secondary winding is connected by means of the center tap 37 to the negative conductor 38 which connects with the thermocouple bus 25 of each thermoelectric system. The extremities of the secondary winding are respectively connected by a pair of

diode rectifiers

40 and 41 to the positive conductor 42 electrically connected to a terminal of the thermostat 33. A filtering capacitor 43 is bridged across the positive and

negative conductors

42 and 38. The thermostat contact 34 is connected directly to the conductor 44 which in turn connects to the positive bus 24 of each of the thermocouple systems. The lower contact 35 is connected to the conductor 44 by way of the limiting resistor 45 whereupon when the bimetal thermostat cools and deflects downwardly, substantially less power is supplied to the thermoelectric systems and the cooling effect thereof is substantially diminished. In this way the temperature within the compartment 4 may be held within the desired range of from 33 to 35 F. It will be understood that the transformer, rectifiers, and resistor will be disposed within the compartment 14.

The embodiment of FIG. 5 contains in addition to or independently of the above described meat storage compartment 4 a thermoelectrically cooled shelf 50 comprising a thermoelectric system as previously described. Said shelf or panel 50 is supported by any suitable insulated brackets 51 to the sides of the inner liner 2 to provide a compartment in the upper portion of chamber 3. In FIG. 6 the N- and P-type semiconductors and the connecting bus bars and conductors have been identified by the numbers previously used. In this arrangement however, the thermocouples are calculated to provide a temperature at the upper aluminum plate 27 of F. whereupon conventional ice trays 52 may be placed to freeze the water contained therein. The lower aluminum plate 27 which comprises the hot side of the thermocouple system has brazed thereto a loop 53 which comprises a loop or portion of the refrigerant evaporator tubing externally of the evaporator 18.1 which serves the compartment 3. This refrigerant circuit arrangement therefore provides in a re frigerator devoted mainly to fresh food storage, adequate ice freezing facility without requiring specialized or secondary refrigerator systems, whereby the normal refrigeration operation proceeds substantially independently of the ice making function. The arrangement of FIG. may be in all respects similar electrically to that shown in FIG. 8 with the possible exception of the elimination of the thermostat for the reason that the ice freezing panel 50 is less susceptible to substantial temperature difference. Therefore, the conductor 42 of FIG. 8 would connect directly to the conductor 44 thereof without the intermediate thermostat and its connections.

In FIG. 7, I have schematically shown in fragmentary perspective a compartment 54 housed partially within the refrigerator door 11 at the lower portion thereof. This arrangement will be in lieu of the arrangement of FIG. 2; and it is not contemplated that the refrigerator would incorporate the meat storage compartment 4. The compartment 54 is designed primarily for the storage of packages of frozen foods and cans of frozen juice concentrate and may comprise any suitable molded plastic structure having a swing-down door 55. The bottom wall of said compartment comprises a thermoelectric system 56 essentially similar to that described in 'FIG. 3 and arranged so that the top wall surface 57 is the cold surface and the bottom wall surface 58 the hot surface. The thermoelectric pile comprising the system 56 is calculated to maintain a temperature of from 0-10 F. within the compartment. A refrigerant loop 60 is attached to the bottom wall 58. Said loop serves the circuit 60.1 which conducts the gaseous refrigerant about the periphery of the door, whereupon the heat of condensation of said gaseous refrigerant maintains the door opening at a temperature to prevent sweating.

While there have been described what are at present considered to be the preferred embodiments of the invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the scope of the invention.

I claim:

1. A refrigerator having a cabinet and a door providing a first thermally insulated cooling chamber, a refrigeration system for cooling such chamber to a temperature a few degrees above the freezing temperature of water, wall means within said cabinet providing a second 5 cooling chamber immediately adjacent said first chamber, means including a plurality of thermocouples providing a cold junction system interiorly of said second chamber and a hot junction system exteriorly thereof but in direct heat-flow relationship to said first chamber, means for electrically energizing said thermocouples to produce a Peltier effect to transfer heat from the interior to the exterior of said second chamber, and means including a condensation-evaporation refrigeration system comprising a closed loop of tubing having a first portion thereof disposed in heat exchange relation with said hot junction system and another portion disposed adjacent to and substantially co-extensive with at least three sides of the door opening of said first chamber to give up heat to wall surfaces circumscribing said opening, the first-named portion of said loop containing a charge of vaporizable refrigerant in the liquid phase, whereby said refrigerant will be evaporated for condensation in the other portion of said loop to donate its heat of condensation to the cabinet wall surfaces traversed thereby.

2. A refrigerator according to claim 1, in which the hot junctions of said thermocouples are in thermally conducting and electrically insulating relationship to a metallic plate comprising a portion of the side wall of said second chamber, and said first loop portion is secured to said plate in heat exchange relation.

3. A refrigerator according to claim 1, in which said second chamber is on the inner wall structure of said door in openly facing relation to said first chamber, the first-named loop portion of said condensation-evaporation refrigeration system is exposed to said first chamber, and the remainder of said system is wholly within the door adjacent the inner wall thereof.

4. A refrigerator having a cabinet and a door providing Wall structures defining a first thermally insulated cooling chamber, a refrigeration system for cooling of said chamber to a temperature a few degrees above the freezing temperature of water, wall means within the confines of said cabinet wall structure providing a second cooling chamber, means including a plurality of thermocouples providing a cold junction system interiorly of said second chamber and a hot junction system exteriorly thereof but in direct heat-flow relationship to said first chamber, means for electrically energizing said thermocouples to produce a Peltier effect to transfer heat from the interior to the exterior of said second chamber, and means for transferring to selected wall portions of said first chamber the heat abstracted from said second chamber, comprising a condensation-evaporation refrigeration system comprising a closed loop of tubing having a portion thereof disposed in heat exchange relation with said hot junction system and another portion disposed adjacent to and in desired heat transfer relationship to said first chamber Wall portions, the first-named portion of said loop containing a charge of vaporizable refrigerant in the liquid phase, whereby said refrigerant will be evaporated for condensation in the other portion of said loop to donate its heat of condensation to the said wall portions.

5. A refrigerator having a cabinet and a door each comprising inner and outer wall structures spaced one from the other by means providing a first thermally insulated cooling chamber, a refrigeration system including an evaporator Within said chamber for cooling the same to a temperature a few degrees above the freezing temperature of water, wall means within said cabinet providing a second cooling chamber, means including a plurality of thermocouples providing a cold junction system interiorly of said second chamber and a hot junction system exteriorly thereof but in direct heat-flow relationship to said first chamber, means for electrically energizing said thermocouples to produce a Peltier effect to transfer heat from the interior to the exterior of said second chamber, and means including a run of tubing of said loop to efiect continuous removal of heat from said thermocouple hot junction.

6. A refrigerator according to claim 5, in which said run of tubing comprises an element of said evaporator.

References Cited in the file of this patent UNITED STATES PATENTS Harris Sept. 8, 1953 Becket Apr. 19, 1960